You could request for the permission of your existing clients to show materials you've done for them in the past as samples for your prospects. Or:

If you're just starting out, then paying your offshore associates to develop materials that you can include in your website as your portfolio (or distribute as samples) is a marketing investment on your part...

I'd like to know how you provide sample work to prospects when you're outsourcing...

Thanks

Audray

I'm a little confused by your question. Do you mean how to show prospective clients work samples or a portfolio when you outsource most of the work.

This is were monitoring and quality assurance comes in.
For those who work in SEO or marketing: Those who outsource usually have project management tools that monitor goals and milestones. These projects and the results of these projects are the ones that you can show to your clients.

Programming, graphic design, content creation: You keep track of your outsourced employees work by keeping a list of links in a portfolio. The portfolio sometimes also serves as a template or guide on the skill and quality of workers you want to hire.